Primary AML blasts generate significantly elevated extracellular superoxide. (A) Representative histograms showing fluorescence of unstained primary AML blasts, MitoSOX-labeled primary AML blasts and MitoSOX-labeled normal human CD34⁺ cells. (B) Summary of MitoSOX mean fluorescence of normal human CD34⁺ cells (n = 5) compared with primary AML blasts (n = 49). The solid horizontal bar represents the mean cohort fluorescence; the dotted horizontal bar indicates the mean + 2 SD boundary. (C) Representative time-course of constitutive superoxide production (×10³ photons/s) of 3 different unstimulated primary AML cell samples compared with that of unstimulated normal human CD34⁺ cells. (D) Summary of total constitutive superoxide production (total photons) by primary AML blasts (n = 61) compared with normal CD34⁺ cells (n = 10). The solid horizontal bar represents the cohort mean; the dotted horizontal bar indicates the mean + 2 SD boundary. Significance of difference was determined using the Mann-Whitney U test. *P < .05.